Github: Enforce expected amount of cxa_atexit registrations

[Sonicadvance1]

On top of the previous PRs.

There is only one registration that I've not been able to track down why
it happens, but it is something to do with std::ostream. This just
ensures in CI that we don't ever register anymore atexit handlers so we
don't regress on crashing on exit.

[Sonicadvance1]

Looks like the bash implementation doesn't work. I don't know bash well enough to know what's wrong. 🤷

[neobrain]

Suggested change

	COUNT = `llvm-objdump -D ${{runner.workspace}}/build/Bin/FEX | grep "__cxa_atexit@plt>$" | wc -l`
	if [ $COUNT -eq 1 ]
	echo "Expected 1 atexit handlers, found $COUNT"
	exit 1
	fi
	COUNT=`llvm-objdump -D ${{runner.workspace}}/build/Bin/FEX | grep '__cxa_atexit@plt>\\$' | wc -l`
	if [ $COUNT -ne 1 ]
	echo "Expected 1 atexit handlers, found $COUNT"
	exit 1
	fi

Something to this effect should be good. Otherwise you might need to open a terminal and run it once to find the last typo.

[crueter]

Suggested change

	working-directory: ${{runner.workspace}}/build
	COUNT=$(llvm-objdump -D build/Bin/FEX | grep '__cxa_atexit@plt>\\$' | wc -l)
	[ "$COUNT" -eq 1 ] || { echo "Expected 1 atexit handlers, found $COUNT"; exit 1; }

Slightly more concise. Also ensure to remove the redundant working-directory and shell directives (cc. #5243 and #5245)